First see how far you are from the router. The further away a device is from a router the weaker the connection will be. A way to fix the distance issue, common on houses with two or more floors, is to use a repeater to enhance the signal on the floor without the router. However that may not be the issue and a solution to try first would be:
1) Go to Control Panel -> Power Settings
2) Click on Change Settings for the Current Active Plan
3) Click on Change Advanced Power Settings
4) Go to Wireless Adapter Settings -> Power Saving Mode
5) Make sure all values are set to maximum performance
6) Click Apply, then Ok and Restart the system